In the prior art, various processes and apparatus have been proposed to produce a texture on printed material. U.S. Pat. No. 3,247,785 to Shultz discloses a method and apparatus for texture embossing a sheet of material. In this patent, a metallic foil layer laminated to a paper backing layer is continually embossed with a textured embossing pattern. A pattern may consist of a series of hills and valleys arranged in a predetermined configuration. By arranging the hills and valleys in various angles relative to each other, a texture embossed pattern can give the appearance of a particular shape on the surface of the material even though the entire foil material is of the same color. However, the patent to Shultz does not recognize registering a plurality of patterns in a predetermined configuration with shapes and/or colors of above a printed image to reflectively enhance the printed image.
U.S. Pat. No. 3,157,559 to Menconi et al. discloses a multi-colored pictorial representation characterized by highlighting effects and a process for making same. In this patent, a pictorial representation is obtained wherein the pictorial representation is broken down by color separation. Striations are formed in the various colored areas with striations in adjacent colored areas extending in different directions to provide the highlighting effect. However, Menconi et al. does not teach or fairly suggest obtaining a density composite from the pictorial representation such that different patterns and different reflectivities may be put in registration within a given color or various shapes depicted in the pictorial representation. Moreover, Menconi et al. does not suggest non-linear patterns for enhancing reflectively such as circles, sinusoidal shapes or the like.
Another prior art process, typically called embossing, imparts a shape to a surface by passing a web of printed material through a pair of embossing rolls to create a three-dimensional effect. The embossing rolls include a plurality of matching male and female patterns which cooperate to form a raised shape on the web.
The embossing rolls are hand crafted by first making a shoe containing a male pattern. The shoe is then worked into the surface of one of the embossing rolls to form a plurality of female patterns therein. The spacing between the plurality of female patterns is also determined by the artisan manipulating the shoe. The spacing generally corresponds to the particular size of the article which is to be embossed by the embossing rolls.
After the female patterns are formed on one of the rolls, this roll is hardened and continually rolled against a soft second embossing roll. Due to the difference in hardness between the rolls, male patterns are formed on the second roll which correspond to the plurality of female patterns on the first roll.
The embossing rolls are then installed into a rotogravure printing press. The embossing rolls form a three-dimensional shape on the surface of the rotogravure printed image.
The method of rotogravure printing and apparatus therefor are well known in the prior art. In rotogravure printing, a printed image is produced using a copper cylinder on which an image has been engraved. The engraved image on the copper cylinder is produced using known methods. In a rotogravure printing press, a web is fed between a series of impression cylinders and engraved printing cylinders. Each of the printing cylinders revolves in ink fountains containing a particular colored ink. The ink is then rolled into the engraved printing cylinder in the fountain. A doctor blade wipes off the superfluous ink, which drops back into the fountain. The web is run against the cylinder utilizing a rubber impression roll of proper durometer to print the image sharp and clear on the web. The rotogravure presses may run multiple colors to print an image having a variety of color tones.
The techniques for developing the cylinders in rotogravure printing are also well known in the art. Typically, an image is broken down into a series of separations to isolate the various colors making up the image. From these color separations, the printing cylinders are engraved either photochemically or electromechanically for reproduction of the various colors used during printing in a rotogravure printing operation.
Drawbacks associated with the prior art techniques such as embossing in combination with rotogravure printing include difficulty in aligning the embossing elements with the printed image on the web. Since the elements on the embossing rolls are not always precisely aligned, registration is difficult to obtain. As a result of variations in spacing, registration between embossing and printing is difficult which leads to increased downtime and scrap during production to correct misalignment.
Further, misalignment of the embossing rolls may also result in cutting or damage to the web or elements on the embossing rolls due to the high hardness of the solid embossing rolls. In addition, the need for hand-crafting the embossing rolls contributes to high capital costs for producing the embossing rolls and printed material therefrom.
The prior art texture embossing methods and apparatus as taught in Shultz or Menconi et al. are disadvantageous in that these processes are limited to texture embossing for a single color or providing a single uniform pattern for a given color in a pictorial representation.
In response to the drawbacks and disadvantages of prior art techniques, a need has developed to provide improved ways to form a pattern, shape or texture on a printed web that provides for an enhancement of shapes and/or colors of a printed image.
In response to this need, the present invention provides an improved process and apparatus for imparting a shape or elements to a web of material having a printed image thereon. The present invention overcomes registration difficulties between prior art embossing and printing by eliminating the need for hand-crafting of the shape or pattern embossing rolls. The present invention also provides a novel reflectivity enhancement of a printed image by forming a plurality of differently shaped elements in the surface of a web. Moreover, the elements are in predetermined registration with shapes, colors or varying densities of the printed image to provide reflective enhancement of the image. The shape of the elements also provides a changing reflective enhancement by reflecting light in different directions depending on the orientation of the reflectively enhanced printed surface.